In a large skillet over medium heat, add a drizzle of olive oil. Once hot, brown the lean ground beef with the chopped onion, stirring until the beef is no longer pink, about 5-7 minutes. Season with salt, pepper, and add the tomato paste and minced garlic, cooking until aromatic, around 1-2 minutes. Stir in the drained Ro-tel diced tomatoes and simmer for 5-10 minutes until thickened.

While the beef mixture simmers, bring a large pot of salted water to a boil. Cook the wide egg noodles according to package instructions until al dente, typically 7-9 minutes. Once cooked, drain the noodles and set them aside in the pot to keep warm, allowing them to absorb a bit of their own steam.

In a medium bowl, whisk together the sour cream, softened cream cheese, and cornstarch until smooth and fully combined.

In a large bowl, combine the cooked noodles, the beef mixture, and the creamy sauce. Gently fold everything together until the noodles are thoroughly coated with the savory mixture.

Preheat your oven to 350°F (175°C). Lightly grease a 9x13-inch baking dish and transfer the combined noodle mixture into it, spreading evenly. Top generously with shredded colby jack cheese.

Place the dish in the preheated oven and bake uncovered for 25-30 minutes until the cheese is bubbling and golden brown on top. Allow it to cool for a few minutes before serving.